My biggest Pet Peeve in FimFiction (And Fan Fiction)

You're a fan of a show. Such a big fan, in fact, that you want to write/read a story about the show. You have this great romance idea for two of the characters. They may be friends, acquaintances, enemies, or never actually interact with one another. Even though there's actually nothing romantic between them in the show, or if there is it's only romantic tension, you still have the idea to put them together. You've got the setting down, the plot just right, everything is perfect.

Except one small snag.
You get to the moment where one character finally begins to realize their feelings for another, and you've got nothing. You forgot to build up why they like each other as friends. Or maybe you've slipped up and forgot to put in that (in the case of M/M or F/F) the character isn't straight. Or really establish the relationship between two characters beyond what was put there by the show. Or build between them something that a person who hasn't seen the show would recognize as the beginning of a romantic relationship.

So what can you do? Your story needs them to fall into a relationship, but it's too late to go back and change it. You ponder deeply, you think at length, and then you do the worst possible thing.

You put a romantic thought in their blissfully unromantic head, and have them wonder "Woah, where did that come from?"

From the context of the story, it's clear from nowhere.
It's as though a thought that would never have crossed their mind decided to detour and cross it.
It's as though some cosmic being forced it into their head.
In short, it come from the writer, who didn't think to plan ahead.
But they aren't necessarily bad writers. They just made a bad, awful, terrible decision.

It's a sign, to me, that the writer either didn't think to, or didn't care to establish the relationship enough that the thought would seem natural to a character.

Has Pinkie taken an interest in showing Fluttershy the depth of her friendship by taking One on One time away from her parties? Has Dash admired Twilight's intelligence as being the "Rainbow Dash of magic"? Have Rarity and Applejack come to the realization that their jobs, though vastly different, require immense amounts of dedication? Yes? Was it established before the romantic point came up in the story? Yes? Then you've got a decent story (at minimum) on your hands!

No? Fine. Shove them together, plant an alien thought in their heads and call it love.
Because why write a story well, when you can just write it?

P.S. A complete side note here. Read "A Beautiful Day in Equestria", a meta-fiction (technically it's listed as "surreal shipping" in which the main character, Twilight, knows that something is wrong and struggles against the narrative. It's basically a fic that knowingly uses the above topic, and puts it on it's head.